Very nice, very clean and professional looking.
I see a few minor issues:
1- Tapping on RESULTS on the sliding menu, I would replace the Toast for a MsgBox, I didn't noticed it after I tried a couple of times.
2- Capture the BACK key, tapping it by mistake exits the app, I would either return to the Main screen or display a "Are you sure you want to exit?" message
3- Move the ABOUT after SETTINGS, it makes sense that way, since the "about" it's just information.
4- Increase the font size a little on THEORY, some people might find it hard to read, same goes for the DISCLAIMER.
5- The CONTACT DEVELOPER and SUGGEST FEATURE should open the email client and not show the list you display, some users might find that confusing.
6- Use Message boxes instead of Toasts in CALCULATOR, like I mentioned above, toasts are easily overlooked.
7- Use the proper word UNTIL instead of TILL.
8- On CALCULATOR, maybe add a CLEAR button, it will make things easier.
9- The ad is not centered when the device is in landscape, look
HERE, there's also a misspelling, you have "...rather then kgs" it should be "...rather THAN kgs"
Keep up the good work.
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